Build a local-first expense ledger with nested categories, reusable item lists, payment-account selection, and immediately visible filtered totals. A user could record groceries by choosing a saved item, amount, account, and optional subcategory in a few taps. The first product should focus narrowly on manual entry speed and household-level analysis rather than bank connectivity or financial advice.

Recent requests across unrelated budgeting products show that detailed manual tracking remains poorly served despite a crowded expense-app market. A narrowly designed product can be tested without costly financial-data integrations.